Spray foam insulation sprayed onto the underside of a roof is now one of the most common reasons a house sale stalls at the mortgage stage. The core problem is that the foam hides the roof timbers, so nobody can see whether they’re sound, and in some roofs it can trap moisture against them. Some lenders won’t lend until there’s evidence the roof is in good order, and in some cases that means spray foam insulation removal. This guide explains why, what the professional bodies say, and what to do whether you’re selling or buying.
What is spray foam insulation?
Spray foam is a polyurethane foam sprayed as a liquid that expands and sets. In homes it has mostly been applied between and over the rafters on the underside of a pitched roof, rather than laid across the loft floor. There are two main types:
- Closed-cell foam sets rigid and dense. The Energy Saving Trust notes it insulates well but isn’t vapour permeable, so moisture can’t travel through it and escape.
- Open-cell foam is softer and more vapour permeable, but less effective as an insulator, so it needs a thicker layer.
It was widely marketed, sometimes through cold calling and high-pressure selling, as a quick way to cut heating bills or “fix” an old roof without replacing the coverings.
Why do mortgage lenders have a problem with spray foam?
There are two connected concerns.
1. Nobody can inspect the roof timbers. Foam sprayed over rafters, battens and the underside of slates or tiles hides the structure completely. A valuer or surveyor can’t see rot, woodworm, failed fixings or past leaks. Lenders lend against the value of the property, and they don’t want to lend against a roof whose condition is unknown.
2. It can trap moisture. Roof timbers stay healthy because they can dry out. Foam applied directly to the underside of an older roof, especially closed-cell foam or foam on an unlined roof or a roof with existing leaks, can seal timber against moisture from leaks or condensation. The Energy Saving Trust describes spraying vapour-impermeable foam directly onto an old and poorly maintained roof as one of the highest-risk insulation options, and warns that rainwater collecting against partly sealed timber will eventually cause it to rot.
Some installations also make it impossible to lift and re-lay slates or tiles for repair, because the foam has glued them together.
What RICS, the PCA and the Energy Saving Trust say
RICS (the Royal Institution of Chartered Surveyors) published a consumer guide to spray foam insulation in March 2023. It advises treating spray foam installation as a significant and fundamental alteration to a home, and getting independent advice from someone commercially separate from the installer and manufacturer. It also explains that spray foam can affect a surveyor’s opinion of value, that a valuer may ask for an independent specialist report, and that owners should keep the full installation paperwork.
The Property Care Association (PCA), working with the Residential Property Surveyors Association and with lenders’ input, produced an inspection protocol for sprayed foam in domestic roofs (the current version is dated March 2023). It gives specialists a structured way to assess whether the foam has increased the risk of timber decay, and what should happen next.
The Energy Saving Trust explains the closed-cell and open-cell distinction and stresses that no insulation should go onto a leaking roof: fix the roof first.
Selling a house with spray foam insulation
If your roof has spray foam, expect it to come up. A buyer’s valuer will often note it, and some lenders will then ask for more information or decline. What helps:
- Gather the paperwork now. RICS recommends keeping the installation contract, any calculations, details of work done to the roof, any guarantee or warranty, and any independent test certificate. Have it ready for the buyer’s lender and solicitor.
- Know which foam was used and how it was applied. Was it open or closed cell? Was it sprayed directly onto the underside of the tiles or onto a breathable membrane? Was a gap left for ventilation?
- Consider an inspection before you market the house. A specialist inspection following the PCA protocol, with small areas opened up where needed to see the timbers, gives buyers and lenders something concrete. It may show the roof is in good order, or tell you early that work is needed.
- Be prepared for a removal discussion. Some lenders will only proceed once foam has been removed and the roof checked.
Buying a house with spray foam insulation
Find out early. Look in the loft on a viewing, ask the agent, and raise it with your broker before you apply. Then:
- Ask for the paperwork listed above. No paperwork is a warning sign.
- Check your lender’s position before you spend on searches and surveys.
- Get a survey that goes into the roof space. Our guide to what a Level 2 survey can’t see is relevant here.
- Factor in the cost of removal and any roof repairs, or negotiate on it. Our guide to using your survey to negotiate explains how.
What a survey can and can’t see
A home survey is a visual, non-invasive inspection. On a roof with spray foam:
| We can usually | We can’t |
|---|---|
| Identify that foam is present and roughly how it’s applied | See the timbers, battens or underside of coverings beneath it |
| Look for staining, cracking, gaps or damp around the foam | Confirm whether there is hidden rot or insect attack |
| Inspect the outside of the roof (from the ground or by drone) for slipped or missing coverings | Cut into the foam during a standard survey |
| Check ventilation at eaves and ridge, and moisture readings on exposed timber | Guarantee the roof’s condition |
Where spray foam is found, the report will say clearly that the roof structure is concealed, explain the risks, and recommend a specialist inspection before you commit. That’s not caution for its own sake; it’s the honest limit of what anyone can see without removing foam.
Spray foam insulation removal: what’s involved?
Removal means cutting and scraping the foam off the rafters, battens and underside of the roof covering, then inspecting the exposed timbers. Points to understand:
- It’s messy, slow work, normally done by a specialist contractor. The foam is cut back, bagged and disposed of.
- Some residue usually remains on timber and the underside of slates or tiles.
- Timbers need inspecting once exposed. That’s when any rot or damage shows up, and it may need repair.
- The roof may need a new membrane or re-covering. If foam was holding slates or tiles in place, or there was no underlay, removal can expose problems that were already there.
- Replacement insulation needs designing so the roof can breathe, often with insulation laid at ceiling level and a ventilated loft.
- Keep evidence. Get a written report from the removal contractor, with dated photographs of the exposed timbers and a description of any repairs. That’s what a lender and buyer will want.
Costs vary widely with roof size, access, the type and thickness of foam, and what’s found underneath. We don’t quote figures for contractors’ work, and you should get more than one quote.
Spray foam in older and listed houses
Older roofs, often slate on timber with no underlay, are the most vulnerable, because they rely on air movement to stay dry. Applying spray foam to a listed building may also need listed building consent; see our guide to listed building surveys. Across the Pennines, with heavy rainfall and many older stone houses, it’s well worth investigating a foamed roof thoroughly rather than hoping for the best.
Independent advice
We sell no insulation, removal or repairs. Our surveyor is a PCA Qualified Technician in damp and timber, so we look closely at what the foam may be doing to the roof and say plainly what can and can’t be seen. For a house with spray foam we usually recommend a Home Survey Level 3 (from £570); where you need a focused look at roof timbers and damp, see our damp and timber surveys. Get in touch with the address and what you know about the installation.
Sources and further reading
- Spray foam insulation: consumer guide — RICS
- RICS release new spray foam consumer guide — RICS
- Spray foam in homes — Property Care Association
- Sprayed Foam Insulation Inspection Protocol (March 2023) — Property Care Association
- Spray foam insulation explained — Energy Saving Trust